An image sensor is a semiconductor element that converts an optical image into an electrical signal.
FIG. 1 is a view showing a state where a photoresist for forming a microlens is patterned according to a fabricating method of an image sensor in the related art, FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1, and FIG. 3 is a cross-sectional view taken along line II-II′ of FIG. 1.
According to the fabricating method of the image sensor in the related art, as shown in FIGS. 1 to 3, microlenses are formed by patterning photoresist patterns 31, 33, and 35 for a microlens on a red color filter 11, a green color filter 13, and a blue color filter 15, respectively.
At this time, there are step differences in the height of the upper surfaces of the red color filter 11, the green color filter 13, and the blue color filter 15. Therefore, a planarization layer 21 is formed on the red color filter 11, the green color filter 13, and the blue color filter 15. Accordingly, the photoresist patterns 31, 33, and 35 are formed on the planarization layer 21.
A thermal processing process such as a thermal reflow process is performed on the photoresist patterns, making it possible to form the image sensor as shown in FIGS. 4 to 6. Here, FIG. 4 is a view showing a state where the microlenses are formed by means of the fabricating method of the image sensor in the related art, FIG. 5 is a cross-sectional view taken along line III-III′ of FIG. 4, and FIG. 6 is a cross-sectional view taken along line IV-IV′ of FIG. 4.
With the fabricating method of the image sensor in the related art, microlenses 41, 43, and 45 having the same thickness and the same shape are formed on the red color filter 11, the green color filter 13, and the blue color filter 15, respectively. In general, blue light has a wavelength band of about 455 nm, green light has a wavelength band of about 555 nm, and red light has a wavelength band of about 655 nm.
FIG. 7 is a view for explaining a state where light incident from the image sensor fabricated according to the fabricating method of the image sensor in the related art is condensed.
With the image sensor in the related art, as shown in FIG. 7, when the thickness and the shape of the microlenses 41, 43, and 45 performing a condensing function on the three color filters 11, 13, and 15 are the same, the positions where the light is focused onto a light receiving unit are different from each other because of the difference of wavelengths according to colors. In the case of blue light with the shortest wavelength, the focus is on the closest position from the microlens 45, in the case of green light, the focus is on the middle from the microlens 45, and in the case of red light, the focus is on the farthest position from the microlens 41. Therefore, the degree of light condensing on light receiving units 51, 53, and 55 formed at the same position is different so that the characteristics of the image sensor is degraded.